ECG depicts the depolarisation and repolarisation processes during the cardiac cycle. In the ECG of a normal healthy individual one of the following waves is not represented.

1. Depolarisation of atria

2. Repolarisation of atria

3. Depolarisation of ventricles

4. Repolarisation of ventricles

(b) A normal ECG represents P-wave atrial depolarisation QRS complex-ventricular depolarisation T-wave ventricular repolarisation. Therefore, atrial repolarisation is not represented is not represented in an electrocardiogram (ECG).